Binary oleogels of β-sitosterol and propyl gallate: Role of the ester group in gelation and stability.

In this study, binary oleogels based on β-sitosterol (Sit) and natural phenolics bearing aromatic hydroxyl groups were developed. Among five screened phenolics (eugenol, propyl gallate (PG), thymol, carvacrol, and resveratrol), only PG formed stable binary oleogels with Sit, specifically at Sit:PG molar ratios ranging from 2:8 to 6:4. All resulting Sit-PG binary oleogels exhibited short needle-like crystals, with hydrogen bonding identified as the primary molecular interaction driving self-assembly. Among these, the 5:5 M ratio (S5P5) showed the highest fractal dimension (Db = 1.7672), the smallest intermolecular spacing and subcell dimensions, and the strongest gel network. Consequently, this formulation also showed the highest storage modulus (7.71 × 105 Pa), viscosity, and thixotropic recovery rate (49.47%), along with excellent oil binding capacity (98.21%) and hardness (8.62 N). These findings identify PG as an effective co-gelator for Sit and provide insights into the design of binary oleogels.